Bootstrap is a free and open-source CSS framework directed at responsive, mobile-first front-end web development. It contains CSS and JavaScript-based design templates for typography, forms, buttons, navigation, and other interface components.
Heroku is a cloud platform as a service (PaaS) supporting several programming languages.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Ruby is an open-source object-oriented programming language.
WEBrick is a lightweight HTTP server library in Ruby, included in the standard library, primarily used for local development and testing of Ruby web applications.